Both maternal and paternal smoking during pregnancy was associated with an increased risk of ADHD in children.Gideon/Flickr

Women who smoke during pregnancy are more likely to have children with attention-deficit/hyperactivity disorder (ADHD), according to a new study from Denmark.

ADHD, according to the Centers for Disease Control and Prevention (CDC) in the US, is a common mental disorder found in children that leads to poor concentration, hyper activity and behavioral problems. An early identification and treatment of the disorder is important, as it can have a negative impact on learning and academic development.

Though the study primarily focused on maternal smoking, researchers warned that nicotine replacement therapies like patches and gums can also pose similar risks to children, Health Day reported.

Women who are pregnant or who are planning for a baby are always recommended to completely abstain from smoking. Countless studies in the past have highlighted many health risks associated with smoking, including cot death, asthma, infertility in sons, low birth weight, infections, obesity, stillbirth, autism, gestational diabetes and low birth weight.

For the new study, researchers selected 84,803 children enrolled in the Danish Birth Cohort. While the prevalence of maternal smoking was determined through interviews, researchers used medical records from different sources to find out ADHD in children and as many as 2,000 children showed signs of ADHD.

Both maternal and paternal smoking during pregnancy was associated with an increased risk of ADHD in children. The risk was highest when both parents smoked (4.2 percent) than only one of the parents smoked. The risk was similar in children of women who smoked (3.4 percent) or reported using nicotine replacement products (3.8 percent) after conceiving the child. However, researchers said that their findings about nicotine replacement therapies are uncertain due to the small number of women (29) who used these products in pregnancy.

"Our findings suggest that exposure to prenatal tobacco smoke, possibly nicotine, may have a prenatal programming effect on the risk of ADHD in children," the authors wrote, according to dailyRX.

The best way to avoid this side-effect is to remain nicotine-free after conceiving the child, the researchers said. "If at all possible, try not to smoke when conceiving," Dr Timothy Wilens, director of the Center for Addiction Medicine and acting chief of child psychiatry at Massachusetts General Hospital in Boston, told Health Day. "If you think you've conceived and you're smoking, it's best to come off the cigarettes as quickly as possible. If you need to use nicotine-replacement therapy, use it for as short a time as possible."

Findings of the study have been reported in Pediatrics.